https://www.webmd.com/digestive-disorders/what-your-gut-bacteria-say-your-health#1
For years, we thought of bacteria as organisms to avoid. It turns out our bodies are already loaded with trillions of bacteria. They help digest food and play an important role in your well-being.
Research suggests your gut bacteria are tied to your probability of things like diabetes, obesity, depression, and colon cancer.
What Are Gut Bacteria?
Living inside of your gut are 300 to 500 different kinds of bacteria containing nearly 2 million genes. Paired with other tiny organisms like viruses and fungi, they make what’s known as the microbiota, or the microbiome.
Like a fingerprint, each person's microbiota is unique: The mix of bacteria in your body is different from everyone else's mix. It’s determined partly by your mother’s microbiota -- the environment that you’re exposed to at birth -- and partly from your diet and lifestyle.
The bacteria live throughout your body, but the ones in your gut may have the biggest impact on your well-being. They line your entire digestive system. Most live in your intestines and colon. They affect everything from your metabolism to your mood to your immune system.
Gut Bacteria and Disease
Research suggests the gut bacteria in healthy people are different from those with certain diseases. People who are sick may have too little or too much of a certain type. Or they may lack a wide variety of bacteria. It’s thought some kinds may protect against ailments, while others may raise the risk.
Scientists have begun to draw links between the following illnesses and the bacteria in your gut:
Obesity, type 2 diabetes, and heart disease: Your gut bacteria affect your body’s metabolism. They determine things like how many calories you get from food and what kinds of nutrients you draw from it. Too much gut bacteria can make you turn fiber into fatty acids. This may cause fat deposits in your liver, which can lead to something called “metabolic syndrome” -- a condition that often leads to type 2 diabetes, heart disease, and obesity.
Inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis: People with these conditions are believed to have lower levels of certain anti-inflammatory gut bacteria. The exact connection is still unclear. But it’s thought that some bacteria may make your body attack your intestines and set the stage for these diseases.